This invention relates generally to a method and apparatus for applying labels to articles, such as bottles and other containers. In particular, the invention is a method and apparatus for applying a transfer label from a series of labels on a web to the curved peripheral surface of an article.
In general, the prior art teaches two broad categories of labeling systems. In the first category are those machines which employ a silk screening process. Typically, these machines utilize a rubber squeegee for wiping ink through a silk screen which bears a label design. The screen is mounted on a movable labeling carriage which is reciprocated by the action of, for example, a double-acting pneumatic motor. Silk screening machines of this type also provide an article support for positioning the article at a labeling station within the machine. The article support must be capable of moving the peripheral surface of the article into and out of pressure engagement with the screen in a plane orthogonal to the plane of motion of the reciprocating labeling carriage. The article support must also allow the article to rotate freely about its longitudinal axis, in order to maintain engagement of the article's curved surface with the screen, as the screen is translated past the labeling station. To perform a labeling operation, the squeegee and article are maintained in alignment and in compression with one another as the screen is translated in the plane of its surface between these two elements. A machine of this type is described in U.S. Pat. No. 3,249,043.
In the second category of labeling systems are those machines which utilize heat transfer labels. Typically, these machines utilize a heating plate for pressure engagement with the upper surface of a web carrying a series of heat transfer labels. The heating plate is secured to the main frame of the machine, and the web travels along a path extending from a supply roll to a take-up roll, both of which rolls are also fixed to the main frame of the machine. The article to be labeled is supported on a movable article support which carries a first drive for rotating the article about its longitudinal axis, a second drive for moving the article support in a direction orthogonal to the plane defined by the heating plate's bottom surface, and a third drive for moving the article support in a direction parallel to the plane defined by the heating plate bottom surface. To accomplish a labeling operation, the curved peripheral surface of the article is brought into pressure engagement with the lower surface of the web using the lower surface of the heating plate as a bearing surface. With the web interposed between the article surface and the heating plate in this manner, the article support is translated in a direction parallel to the heating plate's bottom surface. As the rotating bottle is moved along the lower surface of the stationary web, the heating plate causes a transfer label to be released from the web and bond to the article surface. A machine of this type is described in U.S. Pat. No. 4,502,380.
Machines utilizing heat transfer labels have enjoyed widespread commercial success over the last ten to fifteen years, since they are able to transfer a label comprising a number of colors in pre-established and observable relationship with one another to an article surface in a one-step operation. Conversely, silk screening machines can apply only one color at a time to an article surface. Therefore, where the label contains more than one color, a multi-step operation is necessitated, which requires a number of different silk screens corresponding to the number of different colors contained on the label. Moreover, any error in registration or marring of the label is not detectable until after the label has been applied to the article.
Accordingly, a principal object of the present invention is to provide a method and apparatus for applying heat transfer labels without the disadvantages of the silk screening processes of the prior art. In particular, it is an object of the present invention to provide a labeling apparatus which can be constructed by a simple conversion of the prior art silk screening device.